Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, United States of America.
Division of Basic Sciences, University of Global Health Equity, Butaro, Rwanda.
PLoS One. 2024 Nov 4;19(11):e0309658. doi: 10.1371/journal.pone.0309658. eCollection 2024.
Over the course of the physical activity transition, machines have largely replaced skeletal muscle as the source of work for locomotion and other forms of occupational physical activity in industrial environments. To better characterize this transition and its effect on back muscles and the spine, we tested to what extent typical occupational activities of rural subsistence farmers demand higher magnitudes and increased variability of back muscle activity and spinal loading compared to occupational activities of urban office workers in Rwanda, and whether these differences were associated with back muscle endurance, the dominant risk factor for back pain. Using electromyography, inertial measurement units, and OpenSim musculoskeletal modeling, we measured back muscle activity and spinal loading continuously while participants performed occupational activities for one hour. We measured back muscle endurance using electromyography median frequency analysis. During occupational work, subsistence farmers activate their back muscles and load their spines at 390% higher magnitudes and with 193% greater variability than office workers. Partial correlations accounting for body mass show magnitude and variability response variables are positively associated with back muscle endurance (R = 0.39-0.90 [P < 0.001-0.210] and R = 0.54-0.72 [P = 0.007-0.071], respectively). Body mass is negatively correlated with back muscle endurance (R = -0.60, P = 0.031), suggesting higher back muscle endurance may be also partly attributable to having lower body mass. Because higher back muscle endurance is a major factor that prevents back pain, these results reinforce evidence that under-activating back muscles and under-loading spines at work increases vulnerability to back pain and may be an evolutionary mismatch. As sedentary occupations become more common, there is a need to study the extent to which occupational and leisure time physical activities that increase back muscle endurance helps prevent back pain.
在体力活动转变的过程中，机器在工业环境中很大程度上取代了骨骼肌，成为运动和其他形式的职业体力活动的动力源。为了更好地描述这一转变及其对背部肌肉和脊柱的影响，我们测试了农村自给农民的典型职业活动在多大程度上需要更大的背部肌肉活动幅度和增加的脊柱负荷，以及这些差异是否与背部肌肉耐力有关，背部肌肉耐力是背痛的主要危险因素。我们使用肌电图、惯性测量单元和 OpenSim 肌肉骨骼建模，在参与者进行一小时职业活动的过程中，连续测量背部肌肉活动和脊柱负荷。我们使用肌电图中频分析测量背部肌肉耐力。在职业工作中，自给农民激活背部肌肉和加载脊柱的幅度比办公室工作人员高 390%，变异性高 193%。考虑到体重的偏相关分析显示，幅度和变异性反应变量与背部肌肉耐力呈正相关（R = 0.39-0.90[P < 0.001-0.210]和 R = 0.54-0.72[P = 0.007-0.071]）。体重与背部肌肉耐力呈负相关（R = -0.60，P = 0.031），这表明较高的背部肌肉耐力可能部分归因于较低的体重。由于较高的背部肌肉耐力是预防背痛的主要因素，这些结果进一步证明了在工作中背部肌肉活动不足和脊柱负荷不足会增加背痛的易感性，这可能是一种进化不匹配。随着久坐不动的职业越来越普遍，有必要研究增加背部肌肉耐力的职业和休闲时间体力活动在多大程度上有助于预防背痛。
